For example, WO 2010/038861 A (Patent Literature 1) and WO 2010/038863 A (Patent Literature 2) disclose a multicore fiber having multiple propagating cores in a single fiber.
An optical coupler (connector), which can couple multicore fibers each other with low loss and can be used without loss variation when repeatedly attaching and detaching, is needed for optical communication by using the multicore fibers as a transmission line.
JP 2010-286548 A (Patent Literature 3), JP 2010-286718 A (Patent Literature 4), and JP 2011-158768 A (Patent Literature 5) disclose a method for coupling multicore fibers each other.